Compensating radial work support for an internal centerless grinder



June 17, 1958 R. CANN 2,838,885

COMPENSATING RADIAL WORK SUPPORT FOR AN INTERNAL CENTERLESS GRINDER 2 Sheets-Sheet 1 Filed April 1, 1957 INVENTOR Rowld 01am ATTORNEYS June 17", 1958 CANN 2,838,885

R. COMPENSATING RADIAL WORK SUPPORT FOR AN INTERNAL CENTERLESS GRINDER Filed April 1, 1957 2 Sheets-Sheet 2 INVENTOR Roezld (Jana ATTORNEYS accompanying drawings whereini V Figure l is 'a schematic side elevation illustratingthe 1 United States Patent'Q COMPENSATING RADIAL WORK SUPPORT FOR AN INTERNAL CENTERLESS GRINDER Roald Cann, Weathersfield, Vt., assignor to Bryant Chucking Grinder Company, Springfield, Vt.

Application April 1, 1957, Serial No. 649,765 4 Claims. c1. 51-103 This invention relates to improvements in internal grinding machines of the type wherein an annular workpiece is radially supported on a preformed outside surface for rotation in frictional relationshipto supporting shoes peripherally spaced along the surface, and a tool is applied to its inner periphery to generate an internal surface concen- In internal centerless grinding, typical workpieces, such as raceway rings for anti-friction bearings, must be produced at a fast rate while holding narrow tolerance limits in concentricity and diametrical dimensions. Because of prevailing economic and technological reasons the preformed outside surfaces are allowed to have dimensional variations between successive workpieces and the internal grinder is expected to accept such workpieces at random and produce a hole therein concentric with the preformed, radially supported perimeter. Although this condition of added complication could be wholly or at least partially,

workpieces, any such means have heretofore proven to be u'neconomical. From the foregoing, it follows that in order to accomplish the abovestated results the centers of successive workpieces always must be located at a PIG-1.

defined position irrespective of random diametrical variation between the consecutive workpieces.

It is therefore an object of this invention to provide means for accepting successive workpieces with random remedied by pregaging and classification grouping of variations of the outside diameter, and supporting these workpieces for internal centerless grinding with the centers of the workpiece in predetermined positions.

Another object is to provide a radial work support that automatically compensates for random variations'in outside diameters of successive workpieces.

A further object is to provide a device'wherein the radial support means are arranged in a manner that at least during the final part of the grinding operation the center of the workpiece is located at a controlled predetermined position relative and tool.v

to the contact point between workpiece For a complete understanding of this invention, refer- I enceunay behad to the following'detailed descriptionand radial work support means in relation to the workpiece and tool;

Figure 2 is a side elevation partially in section illustrating a preferred embodiment; and

Figure. 3 is a fragmental view illustrating a modification of the Figure 2 embodiment.

Referring to Figure l, the workpiece W is supported vertically by a fixed shoe V to place the center 0 of a median outside diameter workpiece W on the line of feed F of the tool T. Another shoe H is located on the line of feed F and supports the workpiece horizontally in the 2,838,885 Patented June 17, 1958 ICC path of the feed movement of the tool. atfixed to a member X pivotally mounted at pivot P which is located on a line runningthrough the center .of the workpiece between shoes V and H. The slope of this line is the diagonal in a rectangle with a side A parallel to the feed line and a side B normal thereto, the side A being two times the length of side B. Another shoe S is also carried by member X; this shoe S is spaced peripherally 90 from shoe H and is therefore positioned diametrically opposite shoe V. The three shoes V, H,.and S are located on a'circle having a diameter coincident with a workpiece of median diameter positioned with its center 0 on the feed line F. For the sake of clarity, shoes H and S are shown terminating as edge points, and the differences in workpiece diameters are grossly exaggerated. In reality, these differences are only a few thousands of an inch.

Since member X is free to pivot, the shoes H and S will participate in the movement in a manner dictated by the geometry and arrangement of the parts described aboveytherefore, the movement of shoe S will be two timesthe'extent of the movement of shoe B. By placing a workpiece W with larger than normal diameter in the work support the arm will pivot clockwise and the shoe S will move a distance reflecting the'diametrical difference between W and W and shoe H will, because of the same movement, reflect .the radial difference between W and W. In the new position of member X the shoes H and S together with shoe V now define the periphery of said larger workpiece and, it is found that the center'O' thereof has been displaced to a new position on a line N running through the center 0, and normal to the line of feed F. If instead, a workpiece W" with a diameter less than a normal workpiece is introduced, the same changes in positioning would occur in an opposite sense. The tool T- is shown at a start position of its transverse feed movementwith its righthand edge a fixed distance TF from the aforesaid line N normal to feed direction F. To gen erate a hole the tool edge is moved towards the shoe H a distance equal to the radius of the hole to be generated minus the distance TF. With the centers 0, O, or 0 always located on the normal line N it will be clear that the holes D, D, or D" will have the same diameters irrespectiveof the differences of the preformed outside diameters of W, W, or W, respectively. Thisis due to the pivoted support member which allows each workpiece W, W, or W to be supported with its finished inside diameter the same distance from the normal line at the line of feed F.

Referring to Figure 2 for a preferred embodiment showing a sectional partial upper part of a machine bed 10 on which is supported a headstock 12 including driving and support means for a workpiece W. This headstock isarranged for a transverse feed movement in guide ways, and is actuated by a feed screw 14 journaled in bed 10 and inthreaded'engag'e'ment with a lug on the headstock. A fixed first shoe 16 which is integral with the headstock 12 supports an annular workpiece Won its preformed perimeter. The workpiece W is supported axially by the face of a rotatable driver18, and in frictional relationship by thereto, whereby the rotating movement of the driver is transmitted to the workpiece, and' at the same time a seating'forceisexerted to hold the workpiece against its radial support means as described in the Arms et al. Patent 2,635,395 referred to above. A horizontal rotatable spindle 20 carrying to tool T is located within the inner periphery of an annular workpiece W for feed movement along line of feed F. A member 22 is supported on the headstock for rocking movement and this member carries a second shoe 24 the face of which supports the workpiece on its perimeter substantially in line with the feed movement. Also carried by the mmeber 22 is a sensing element in the form of a third shoe 26 located pe- The shoe H is 3 i ripherally removed 90 from said second shoe and diametrically opposite the first shoe 16. These three shoes define a circle coincident with the outside periphery of a w rkpiece which, when of median diameter, will have its center on the feed line. The fulcrum of the pivot for the rockable member 22 is located at a point on a line as described in connection with Figure 1. Said pivot is preferably in the form of crossed reeds 28 having one degree of freedom. Extending from the member is a lug 30, and a spring 34 is interposed between this lug and a projection 32 on the headstock to consistently bias member 22 to rock an adjustable distance, limited when a screw 36 in a lug 38 on the headstock abuts lug 30. Another screw 40in lug 42, also on the headstock, limits rocking movement in the opposite direction.

' The operation of the device is as follows: The tool is moved from the grinding zone in an axial longitudinal direction to'allow a workpiece to be loaded or removed. Without a workpiece present the member 22 will, because of the spring bias, rock a distance limited by screw 36 adjusted to prevent the shoe 26 from interfering with the loading of a workpiece. A workpiece is now placed with one of its end faces against the continuously rotating driver, to be located axially and rotated thereby in direction indicated by the arrows. By known means, such as described in the Arms et al. Patent 2,635,395 referred to above, a seating force acts to urge the outside surface of theworkpiece against the radial supporting shoes. Shoe 16 is fixed positively preventing the workpiece from moving in a direction normal to the line of feed, whereas spring 34 permits rocking movement of member 22 and shoe 26; hence, the workpiece may be displaced parallel to the line of feed. The stiffness and initial compression of spring 34 are selected so as to permit the seating force to move the workpiece and member 22 only enough to insure contact at both shoes .26 and 24 but not so much as to lose contact at shoe 26. The tool is now reintroduced in the grinding zone at a position indicated by a broken line circle and the feed movement in the direction of arrow at F may start. The force of the tool feed is then added to the seating force and will overcome the spring force to rock the member 22 clockwise until the ing 30 contacts screw 40 which is adjusted to limit the pivotal movement so that shoe 26 retains contact with the outside surface of the largest diameter workpiece acceptable for grinding, while all'smaller workpieces during this phase will be out of contact with shoe 26. Towards the end of the grinding operation the infeed rate is slowed down and consequently the grinding force acting against the shoe 24 becomes less and the force of spring 34 overcomes the grinding force and urges member 22 counter-clockwise until shoe 26 contacts the outside surface of the workpiece with the result that shoe 24 will move the workpiece to the left placing its center on the line N. This arrangement effectively compensates for variations in outside diameter between successive workpieces.

Figure 3 is a fragmental view of a modification of the embodiment shown in Figure 2 wherein the fixedshoe 16 thereof has been replaced by two angularly spaced fixed shoes 15 and 17. The line N is the bisector of the angle between the points of contact of the workpiece with the shoes 15, 17 and is normal to the line of feed F. This variation in arrangement of the fixed radial supports results in a variation in the operation: When the greater grinding force in the first part of the grinding process compels the member 22 to rock to the position limited by screw 40, the workpiece is lifted away from shoe 15 and will be seated only againstshoes 17 and 24 except in the case of the largest acceptable workpiece which will always retain contact with all shoes. In the last part of the grinding process when the grinding force is less than the spring force, the workpiece will also be seated against shoe 15, thus positively locating the center of the workpiece on the intersecting line N which runs through the point of contact between the work-piece and shoe 26.

Means other than the rocking member X supporting shoes H and S for proportional displacement can be employed and such means fall within the scope of this invention so long as the kinetics of motion of the contact points of H and S as above described is fulfilled, where the amplitude of oscillation of point H always is half that of point 8. Therefore, other embodiments will become apparent to those skilled in the art and this invention is limited only by the scope of the appended claims.

What I claim is:

1. In an internal grinding machine, including a headstock supporting a rotatable workdriver, a tool in working relationship to the interior of an annular workpiece on which an internal surface is to be generated concentric with a preformed external surface of said workpiece, means to impart a relative transverse motion between the axes of said .tool and workdriver along a line of feed; a work-supporting apparatus comprising: first, second, and third shoes for radiallysupporting a workpiece on said preformed surface and in frictional relationship thereto, said shoes being arranged in predetermined relative positions defining a periphery of a circle corresponding to a median outside diameter workpiece; means rigidly c0n- .necting said first shoe to said headstock; a rockable member carrying said second and third shoes peripherally spaced in relative fixed positions, said second shoe being located on said line of feed and said first and third shoe being located diametrically opposite each other; said rockable member being pivoted about a point located on a line running through the center of amedian diameter workpiece and between said first and second shoe, said line being a diagonal in a rectangle having one side parallel to said line of feed of a length two times the length of the other side. normal thereto.

, 2. A device as defined in claim 1 wherein said periphery of a median diameter of a circle is defined by a predetermined position of said member, and when said member is rocked in one direction a larger diameter is defined, and

when said member is rocked in opposite direction a lesser diameter is defined.

3. A device as defined in claim .2 including springmeans t-o biassaid rockablemember in said direction toward the said lesser diameter. 7

4. A device as defined in claim 3 including means adjustable to limit said rocking movement to a predetermined amount.

References Cited in the file of this patent UNITED STATES PATENTS 

